Pick holder and fixing sleeve for an extraction machine

ABSTRACT

A pick box (3) and sleeve (6) combination comprises a sleeve-receiving aperture (5) in the box (3), with the sleeve (6) located in the aperture (5) and adapted, in use, to receive the shank (17) of a mineral cutter pick (7). A zone (33) of differential area is provided between the external periphery of the sleeve (6) and the aperture (5). A fluid sealing ring (29) is located to each side of the zone (33) of differential area, and a hydraulic fluid entry bore (30) is located intermediate the two sealing rings (29) and is in fluid flow communication with the zone (33), whereby upon admission of hydraulic fluid under sufficient pressure to the zone (33) via the entry bore, the fluid, being confined by the sealing rings (29), effects hydraulic, axial displacement of the sleeve (6) with respect to the box (3). The invention also includes a mineral cutting drum (1) provided with a plurality of such pick and box combinations, and also to a machine provided with at least one such drum.

This invention relates to a pick box and liner sleeve combination,adapted to receive the shank of a replaceable, mineral cutter pick, andto a mineral cutter drum provided with such a pick box, as are usedextensively in mineral mining operations, in tunnelling operations, inquarrying operations, and in so-called road planing operations.

It is known to insert a replaceable liner sleeve (also known as anadaptor) into a circular section aperture of a pick box, into whichliner sleeve is fitted the shank of the pick, so that the sleeve isinterposed between the aperture of the pick box and the shank of thepick. The advantage of a liner sleeve is that in-service wear (whichoccurs due to pick and/or sleeve rotation and impaction) is inflicted onthe liner sleeve rather than the box, because when wear has occurred tosuch an extent that a pick shank cannot be retained satisfactorily, theworn sleeve may be removed and replaced by a fresh sleeve, which avoidsthe need to remove the associated cutting drum to a safe zone of a mine,or even out of the mine, so that a damaged pick box may be removed and afresh pick box welded in place. Furthermore, sleeve removal may benecessary not because the sleeve is damaged, but because a pick has beenbroken off, and its shank remains in the sleeve.

Ideally, the sleeve should be a non-rotating, and hence tight, fit tominimise premature wear, but difficulties are however encountered inremoving "tight" liner sleeves, as these have usually been firmlyimpacted in the aperture of the pick box due to loading which occur inservice. Thus, currently, miners are obliged to employ tools such asscrew-jacks and/or hydraulic jack for insitu removal of a tight sleeve,assuming the box is of open construction, whereby the rear of the sleeveis exposed and hence engageable by the screw-jack. Screw-jack operationin the confines of a mineral face on a rotary cutter drum provided withsay 50 picks, is an awkward and time consuming operation, with loss ofmineral production until the cutter drum is ready for service. With aclosed box, screw-jack removal is impossible. Frequently, sleeveextraction difficulties, which difficulties themselves sometimes lead tothe need to remove the cutting drum from the mining machine to a safearea, or even out of the mine, for the burning-off of pick boxes thathouse liner sleeves that cannot be extracted--the very action that theuse of a liner sleeve seeks to avoid. Hence, an alternative option hasbeen to provide loose-fit liner sleeves and to accept the disadvantagesof premature wear.

Sleeve extraction has been a long recognised problem with, to date, nosatisfactory solution. Thus, in 1979, in DE 2915510, the VOEST companyproposed the introduction of a lubricant being the outer periphery of asleeve of constant external diameter and the sleeve-receiving bore ofthe pick box.

In contrast to the constant diameter sleeve of VOEST, a stepped sleevepositively retained mechanically in the sleeve-receiving bore of thepick box by a roll pin is described in U.S. Pat. No. 4,678,238 of theFansteel but Applicants are unaware whether the Fansteel system has everbeen used in service. In the Fansteel system, which addresses theproblem of pick cooling to minimise metallurgical damage--as the picksfrequently "glow" in action with a tendency for spontaneous methaneignition in coal mining--and also to wash dust and debris away from thepick by used cooling water existing as a spray from an outlet bore ofthe sleeve.

A basic object of the present invention is to provide a pick box andsleeve combination, in which the sleeve can be readily and quicklyremoved, e.g. whilst located at an underground mineral face.

According to a first aspect of the present invention there is provided apick box and sleeve combination comprising;

(i) a sleeve-receiving aperture in the box;

(ii) a replaceable liner sleeve located in the aperture and adapted, inuse, to receive the shank of a mineral cutter pick;

(iii) a zone of differential area provided between the externalperiphery of the sleeve and the aperture;

(iv) a fluid seal located to each side of the zone of differential area;and

(v) a hydraulic fluid entry bore located intermediate the two fluidseals and in fluid flow communication with the zone of differentialarea, whereby upon admission of hydraulic fluid under sufficientpressure to the zone of differential area via the entry bore, the fluid,being confined by the seals, effects hydraulic axial displacement of thesleeve with respect to the box.

According to a second aspect of the invention there is provided amineral cutting drum provided with a plurality of pick boxes inaccordance with the first aspect.

According to a third aspect of the invention there is provided amachine, such as a mining or tunnelling machine, incorporating at leastone mineral cutting drum in accordance with the second aspect.

Thus, in accordance with the invention the sleeve is initially axiallydisplaceable hydraulically as a first step (until the outermost fluidseal exits the aperture) in the extraction process, with the hydraulicpressure not only tending to compress the sleeve and hence slightlyreducing its external diameter and/or tending to expand the box andhence slightly increasing the aperture diameters The hydraulic actionthus has the effect of cracking the retaining forces between theexternal periphery of the sleeve and the aperture of the box, andthereafter a simple extraction tool, such as a screwdriver, may engagethe sleeve to complete the extraction process.

In practice, the fluid entry bore may itself have an inlet end closedoff by a hydraulic adaptor, whereby the simple application of a greasegun, or other hand pump, to the hydraulic adaptor achieves hydraulic,axial displacement of the sleeve. Alternatively, the inlet end of thefluid entry bore maybe screw-threaded, so that a screw-threaded endfitting of a hose line maybe screwed into the inlet end of the fluidentry bore. With this last mentioned arrangement, debris ingress intothe inlet end of the fluid entry bore may be prevented by insertion of ascrew threaded plug, which is removable to enable hydraulic displacementto be effected. Alternatively, if a source of pressure fluid, such asthe water/oil emulsion coventionally employed to power hydraulic rams,or high pressure water, is available, then this source may be connectedto the individual fluid supply bores, as typically some 50 to 80 pickboxes would be provided on a rotary cutting head.

The fluid seals may take the form of "O"-rings located in grooves.

The invention will now be described in greater detail, by way ofexample, with reference to the accompanying drawings, in which:

FIG. 1 shows a pick box in accordance with a first aspect of theinvention welded to a drum in accordance with the second aspect of theinvention;

FIG. 2 corresponds to FIG. 1 but shows the pick removed prior tocommencement of the sleeve extraction process;

FIG. 3 corresponds to FIG. 2 but shows the sleeve about to be removed;

FIG. 4 corresponds to FIG. 3 but shows the sleeve after hydraulicdisplacement, as the first step in the extraction process;

FIG. 5 corresponds to FIGS. 1 to 3, but shows a second embodiment ofpick box; and

FIG. 6 is a section on the line VI--VI of FIG. 5.

In FIG. 1, a rotary mineral cutter drum 1 is mounted on a mining machine(not shown). To external periphery 2 of the drum is welded a pluralityof pick boxes, one only shown at 3 secured by weld metal 4.

In FIGS. 1 to 4, each pick box 3 is provided with a circular sectionaperture 5 into which is fitted a replaceable liner sleeve 6 into whichis fitted a replaceable mineral cutter pick 7, the pick sleeve andaperture having co-incident longitudinal axes 8, 9 and 10 respectively.Penetration of the sleeve 6 is limited by underside 11 of an integralcollar 12 of the sleeve engaging an outer surface 13 of the pick box 3,whilst the sleeve 6 has a circular aperture 40.

The pick 7 has a head 14 which is provided at one end with a carbide tip15 and at the other end with a circumferential groove 16 for engagementby a mechanical extraction tool (not shown); The head 14 is integralwith a circular section shank 17 adapted to be fitted by hand into thesleeve aperture 40, and being provided with a circumferential groove 18in which is located a compressable spring ring 19 for pick retention.

All the above features are known.

In accordance with the invention the aperture 5 is provided with a stepat 20 e.g. at 45° to longitudinal axis 10, the step 20 separating asmaller diameter length 21 from a larger diameter length 22.Correspondingly, external periphery 23 of the sleeve 6 is provided witha step 24 also at 45° to longitudinal axis 9 to separate a smallerdiameter inner length 25 from a larger diameter outer length 26. Thus,the steps 20 and 24 define an annular zone 33 of differential area.

To each side of the step 24, the sleeve 6 is provided with acircumferential groove 27, each housing a fluid seal in the form of aninner "O"-ring 28 and an outer "O"-ring 29, each "O"-ring sealinglyengaging respectively the aperture lengths 21 and 22, whilst, when theunderside 11 of the collar 12 engages the surface 13, the steps 20 and24 also engage, or are slightly spaced from one another.

The pick box 3 is also provided with a fluid entry bore 30 having aninlet end 31 counterbored and screw-threaded to receive a removablescrew-threaded plug 32. At its other end the fluid entry bore is openand in fluid flow engagement with the zone 33 of differential areabetween the aperture 5 and the external periphery 23 of the sleeve 6.

The "in service" position is indicated in FIG. 1, with a pick 7 fittedinto a sleeve 6 in turn fitted into the aperture 5 of a pick box 3.

When pick replacement is required, the pick 7 is extracted in theconventional manner by a screwdriver etc., being engaged in the groove16, to lever the pick from the sleeve. This is the situation illustratedin FIG. 2.

When additionally or alternatively replacement of the sleeve 6 is alsorequired, then in accordance with the invention, the plug 32 is removed,as illustrated in FIG. 2, and into the inlet end 31 is screwed ahydraulic adaptor 34, as illustrated in FIG. 3. In turn, an end fitting35 of a hydraulic fluid supply line 36, is screwed into the hydraulicadaptor 34 and hydraulic fluid, e.g. a water/oil emulsion, as is readilyavailable in mines for activating hydraulically powered roof supports,is applied. This provides pressure fluid to the zone 33 of thedifferential area provided by steps 20 and 24 result in the sleeve 6being jacked out of the aperture 5 by being axially displaced as isillustrated in FIG. 4. When the outer "O"-ring 29 exits the outer length22 of the aperture 5, the effect of hydraulic pressure within the zone33 of differential area is lost, and the first stage of sleeveextraction is finished. Total sleeve extraction may then be effected bya screw-driver etc., engaging the underside 11 of the collar 12 to leverthe sleeve 6 from the aperture 5.

After shutting off the fluid flow the end fitting 35 is disconnected andthe hydraulic adaptor 34 is replaced by the plug 32.

This process is of course repeated at every pick box of a cutting drumwhere sleeve replacement is required.

The embodiment of pick box 3 illustrated in FIGS. 1 to 4 is "open" inthat a slot 37 is provided whereby end 38 of the pick shank 17 mayengage an anvil portion 39 of the pick box 3, whereby the loading on thepick 7 in service is distributed between the anvil portion 39 and, viathe sleeve 6, the leading end of the pick box 3. The slot 37 howeverprovides access to the end of the sleeve 6 remote from the collar 12.

However, the embodiment of pick box 3A illustrated in FIGS. 5 and 6 isof a "closed" type, in that no slot 37 is provided and consequently thepresent invention is particularly suited to this type of pick box. Alsoin contrast to FIGS. 1 to 4, the aperture 5A in the pick box 3A isrectangular, to receive a sleeve 6A with a rectangular externalperiphery. Furthermore, FIG. 6 illustrates the possiblity of theaperture 40A of the sleeve 6A being rectangular, to receive arectangular shank 17A of an industry-standard pick.

I claim:
 1. A pick box and sleeve combination comprising:(i) a sleeve-receiving aperture in the box; (ii) a replaceable liner sleeve located in the aperture and adapted, in use, to receive the shank of a mineral cutter pick; (iii) a zone of differential area provided between the external periphery of the sleeve and the aperture; (iv) a fluid seal located to each side of the zone of differential area; and (v) a hydraulic fluid entry bore located intermediate the two fluid seals and in fluid flow communication with the zone of differential area, whereby upon admission of hydraulic fluid under sufficient pressure to the zone of differential area via the entry bore, the fluid, being confined by the seals, effects hydraulic axial displacement of the sleeve with respect to the box.
 2. A combination as claimed in claim 1 wherein the sleeve-receiving aperture in the box is circular.
 3. A combination as claimed in claim 1 wherein the sleeve receiving aperture in the box is non-circular.
 4. A combination as claimed in claim 1, wherein the liner sleeve has a circular aperture to receive a circular section pick shank.
 5. A combination as claimed in any one of claims 1 to 3, wherein the liner sleeve has a rectangular aperture to receive a rectangular section pick shank.
 6. A combination as received in claim 1, wherein the zone of differential area is provided by a step in the box aperture and by a step in the externally periphery of the sleeve.
 7. A combination as claimed in claim 6, wherein the step of the aperature is at approximately 45° to a longitudinal axis of the aperture.
 8. A combination as claimed in claim 6, wherein the step of the sleeve is at approximately 45° to a longitudinal axis of the sleeve.
 9. A combination as defined in claim 1, wherein the fluid entry bore has an inlet end which is screw-threaded.
 10. A combination as claimed in claim 9, wherein the screw-threaded inlet end is provided with a removable, screw-threaded plug.
 11. A combination as claimed in claim 1, wherein each fluid seal is defined by a sealing ring.
 12. A combination as claimed in claim 11, wherein the sealing rings are housed in peripheral grooves provided in the external periphery of the sleeve.
 13. A mineral cutter drum provided with a plurality of pick box and sleeve combinations, as defined in claim
 1. 14. A mining machine provided with at least one mineral cutter drum as defined in claim
 13. 